San Francisco's proposed $1 billion-plus Central Subway that would bring light-rail service into Chinatown is a costly investment that would do little to address future transit needs, according to an independent study commissioned by the city's Municipal Transportation Agency.

City officials dispute that assessment, arguing that the project would help ease congestion on traffic-clogged streets.

Engineering consultant Thomas Matoff, the city's former director of transit planning who was tapped to analyze the project, said that if the goal is to efficiently improve service, the Central Subway plan falls short.

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"As proposed," Matoff wrote, "this project does not appear to do that -- it promises to combine high capital costs with higher operating costs and ... does not, apparently, effectively meet the market needs in the corridor it is intended to serve."

The proposed subway would connect to the new T-Third line, which serves the city's southeastern neighborhoods and opened for limited service this month.

The 1.7-mile Chinatown extension would add four stops: an aboveground platform on Fourth Street near Brannan Street and three underground stations near Moscone Center, Union Square and the heart of Chinatown. Eventually, the line could be extended into North Beach and the Embarcadero.

Planners estimate that the Chinatown extension, years in the works, would be used by more than 20,000 riders a day. The goal is to open it in 2015.

The federal government has committed $762 million to the project. A combination of state and local money, including sales tax and bond revenue, is expected to fund the remainder.

Next month, city officials are expected to find out whether the proposed project will remain on the federal funding list; there is no indication that it will be removed.

"This is a good project that has a lot of community support," said Nathaniel Ford, who runs the Municipal Transportation Agency. "At this point, we are seeing how we can make it better."

House Speaker Nancy Pelosi, D-San Francisco, has long championed the project that resulted, in part, from the demolition of the Embarcadero Freeway after the 1989 Loma Prieta earthquake. The freeway had provided a conduit into Chinatown and North Beach, and neighborhood business leaders fought an unsuccessful battle to save it.

While the proposed subway would not replace the freeway, its boosters, including Chinatown political powerhouse Rose Pak of the Chinese Chamber of Commerce, say it would benefit local businesses and residents.

"To my mind, the ivory tower consultant was totally ignorant of the on-the-ground realities of Chinatown and San Francisco," said Board of Supervisors PresidentAaron Peskin, who represents Chinatown and surrounding neighborhoods in the northeast sector of the city.

Matoff was not available for comment. His report, issued in April, only recently surfaced publicly and was distributed to the Municipal Transportation Agency's governing board Thursday.

Since the report was written, the plan has been reworked in part to address some of Matoff's concerns. For example, stations have been redesigned to limit the distance people would have to walk to transfer from the new subway line to another Municipal Railway light-rail line or BART.

Agency officials believe they have found ways to shave about $130 million off the previous $1.4 billion cost estimate. Among the ideas: Using two tunnel-boring machines instead of one to save time and money, and reducing the size of stations and boarding platforms. However, shorter platforms require shorter trains, which in turn would limit capacity.

A more detailed financial analysis is under way to see whether the new cost estimates hold up, said project manager John Funghi. Even if it does, the project still faces a funding gap of about $86 million -- an amount that Funghi said isn't insurmountable.

Mayor Gavin Newsom, who inherited the project when he took office in 2004, said he is committed to keeping costs under control. "This will not be a Big Dig redux," he said, referring to Boston's underground roadway that came in billions of dollars over budget.

Matoff suggested in his report that the Municipal Transportation Agency's Central Subway vision is shortsighted.

Among his concerns: the decision to not design a tunnel that could accommodate both trains and buses, which would allow buses to bypass the congested surface streets; the agency's continued insistence to use "high-platform" vehicles that slow boardings because people must step up into the busess and trains; and the location of the Union Square station that "may make a future Geary light-rail line (connection) more expensive."

"There is no question that the corridor needs a subway. The northeast corner of San Francisco has the highest (population) density of any part of the country west of Chicago," said Gabriel Metcalf, executive director of SPUR. "But they don't have the plan right yet. There are flaws. They have a lot more work to do."

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